Assessment of Nepal Consumer Needs, Preferences and Willingness to Pay for Improved Cookstoves: Controlled Cooking Test Results
Prepared for Winrock International by:
Berkeley Air Monitoring Group
April 2015
Table of Contents
Table of Contents .................................................................................................................................... 2
List of Tables ........................................................................................................................................... 3
List of Figures .......................................................................................................................................... 3
Authors and Acknowledgements ............................................................................................................ 4
Report Authors .................................................................................................................................... 4
Field Team ........................................................................................................................................... 4
Support and Acknowledgements ........................................................................................................ 4
Executive Summary ................................................................................................................................. 5
1. Introduction .................................................................................................................................... 6
1.1 Background and Purpose ........................................................................................................ 6
1.2 Study Location ......................................................................................................................... 6
2. Methods .......................................................................................................................................... 7
2.1 Study Overview ....................................................................................................................... 7
2.2 Food and Pots ......................................................................................................................... 7
2.3 Fuel .......................................................................................................................................... 8
2.4 Description of Cookstoves ...................................................................................................... 9
2.5 Quality Control and Assurance ............................................................................................. 12
3. Results ........................................................................................................................................... 13
3.1 Specific Consumption ............................................................................................................ 13
3.2 Cooking Time ......................................................................................................................... 14
3.3 Firepower .............................................................................................................................. 15
4. Implications for field study ........................................................................................................... 17
5. References .................................................................................................................................... 18
6. Appendices .................................................................................................................................... 19
6.1 Daily Scheduling Matrix ........................................................................................................ 19
6.2 Standard Meal Details ........................................................................................................... 20
6.3 Wood Moisture Sampling Form ............................................................................................ 20
6.4 Scale Calibration and Maintenance ...................................................................................... 21
6.5 Field Sampling Form .............................................................................................................. 22
6.6 Field team ............................................................................................................................. 23
2 Controlled Cooking Test Results
3 Controlled Cooking Test Results
List of Tables
Table 1. Summary of CCT fuel consumption and cooking time results, showing the means (± 1
standard deviation) and percentage differences versus the traditional chulho. ................................... 5
Table 3. Specifications and photos of stove types. ............................................................................... 10
Table 4. Summary statistics of the specific consumption estimates from the CCTs. Bolded differences
and p‐values indicate statistical significance. ....................................................................................... 13
Table 5. Summary statistics of the cooking time estimates from the CCTs. Bolded differences and p‐
values indicate statistical significance. ................................................................................................. 15
Table 6. Summary statistics of the firepower estimates from the CCTs. Bolded differences and p‐
values indicate statistical significance. ................................................................................................. 16
Table 7. Example of scale maintenance database (data from day 1 of CCTs shown). .......................... 21
List of Figures
Figure 3. Vegetables and spices on aluminum plates (left), a field technician pre‐weighing daal
(right). ..................................................................................................................................................... 8
Figure 4. Aluminum wok for vegetables (far left), aluminum pot with lid for rice (middle), and
pressure cooker for daal (right). ............................................................................................................. 8
Figure 6. Boxplots showing the distribution of specific consumption for each stove. A guide to the
box plot can be found in the lower right hand corner of the figure. .................................................... 14
Figure 7. Boxplots showing the distribution of cooking time for each stove. A guide to the box plot
can be found in the lower right hand corner of the figure. .................................................................. 15
Figure 8. Boxplots showing the distribution of firepower for each stove. A guide to the box plot can
be found in the lower right hand corner of the figure. ........................................................................ 16
4 Controlled Cooking Test Results
Authors and Acknowledgements
Report Authors
Michael Johnson, Berkeley Air Monitoring Group Samantha Delapena, Berkeley Air Monitoring Group David Pennise, Berkeley Air Monitoring Group Elisa Derby, Winrock International Rabin Shrestha, Winrock International ‐ Nepal Karuna Bajracharya, Alternative Energy Promotion Center Bijaya Raj Khanal, Renewable Energy Test Station Shovana Maharjan, Centre for Rural Technology ‐ Nepal
Field Team
Michael Johnson, Berkeley Air Monitoring Group, Technical Oversight Samantha Delapena, Berkeley Air Monitoring Group, Manager Karabi Dutta, Winrock International Contractor, Manager Rabin Shrestha, Winrock International ‐ Nepal, Data and Field Technician Deenbandhu Parajuli, Renewable Energy Test Station, Field Technician Bijaya Raj Khanal, Renewable Energy Test Station, Field Technician Nisha Jaishwal, Alternative Energy Promotion Center, Field Technician Shovana Maharjan, Centre for Rural Technology ‐ Nepal, Field Technician
Support and Acknowledgements
This project was funded by the United States Agency for International Development‐funded WASHplus project (AID‐OAA‐A‐10‐00040). The authors’ views expressed in this publication do not necessarily reflect the views of FHI360, Winrock International, the WASHplus project, the United States Agency for International Development or the United States Government. This report is a result of hard work from several organization and individuals, whose valuable contributions made this project possible. We thank the staff from the Renewable Energy Test Station and the Alternative Energy Promotion Center who assisted in coordinating and hosting the study, as well as the dishwashers and food collectors. A special thanks to Maheshwar Poudel, who worked exceptionally hard to chop wood, maintain the testing area, and support the field team. We extend our greatest thanks to the cooks, who worked tirelessly during this study; Phulmati Darai, Apsara Subedi, Surya Maya Tamang, Uttar Maya Tamang, Laxmi Pariyar, Dil Kumari Gurung, Nila Ghimire, Subhadra Tamang, Nanu Ghatani, and Nima Lama.
5 Controlled Cooking Test Results
Executive Summary
This study aimed to determine the relative fuel efficiency of cookstoves that are being evaluated as
part of the United States Agency for International Development‐funded WASHplus project:
Assessment of Nepal Consumer Needs, Preferences and Willingness to Pay for Improved Cookstoves.
This study used the Controlled Cooking Test (CCT), which involves preparing a standardized regional
meal to determine the relative fuel efficiency and time demands of different stoves. The primary
output metrics are specific fuel consumption (grams wood/kilogram cooked food) and cooking time.
Testing was conducted over seven days at The Renewable Energy Test Station (RETS) in Lalitpur,
Nepal, with technicians from RETS, the Alternative Energy Promotion Center (AEPC), Center for
Renewable Energy / Nepal (CRT/N), Winrock International, and Ber
A total of 168 CCTs were completed by eight cooks recruited from
The baseline technology was a three‐stone fire and the five new st
Burner Wood Stove with Chimney, Eco‐Chula XXL, AEPC‐promoted
Field Dragon, and the Greenway Jumbo. The main findings are pres
All five of the manufactured stoves had significantly lower
the traditional chulho, with savings ranging from 29 to 47
The Eco‐Chulha and the Xunda demonstrated the highest f
respectively, while the local chimney stove had the lowest
Time savings were also significant, with mean cooking time
time than traditional chulho, which required 64 minutes o
The local chimney stove and Prakti stove, the only two pot
of time to prepare a meal at 43 and 50 minutes, respective
Table 1 summarizes the quantitative stove performance results for
shows the averages (means) and the standard deviations, along wi
compared to the traditional chulho. All differences in fuel consump
significant (p<0.01) using an unpaired Student’s t‐test.
keley Air Monitoring Group (BA).
villages outside of Kathmandu.
oves were the Prakti Double
local mud‐chimney stove, Xunda
ented below:
specific fuel consumption than
%.
uel efficiency, saving 47 and 45%,
fuel savings (29%).
s ranging from 15 to 33% less
n average.
stoves, required the least amount
ly.
each of the six stoves. The table
th the percent differences
tion and cooking time were
Table 1. Summary of CCT fuel consumption and cooking time results, showing the means (± 1 standard deviation) and percentage differences versus the traditional chulho.
Trad Chulho
Greenway Prakti Xunda Eco‐Chulha
Local chimney stove
Number of tests 28 28 28 28 28 28
Specific consumption (g wood / kg food) 328±56 197±36 197±26 179±37 173±22 234±30
% difference from traditional chulho NA 40 40 46 47 29
Cooking time (minutes) 64±8 55±7 50±9 54±6 55±9 43±7
% difference from traditional chulho NA 15 23 16 15 33
6 Controlled Cooking Test Results
1. Introduction
1.1 Background and Purpose
This study was conducted as part of the United States Agency for International Development (USAID)
–funded WASHplus project: Assessment of Nepal Consumer Needs, Preferences and Willingness to
Pay for Improved Cookstoves. The larger WASHplus cookstoves project in Nepal is seeking to
determine what “marketing mix”, the strategic combination of stoves, pricing, distribution and
promotion approaches are most likely to result in Nepalese households adopting and consistently
using high performing stoves. This study specifically assessed stoves with the Controlled Cooking
Test (CCT) to ensure that the stoves being evaluated for the larger study can provide fuel, and
potentially, time savings benefits under typical Nepalese cooking conditions.
The CCT is a standardized, commonly used protocol in the household energy field for assessing stove
performance (Bailis, 2007). The CCT yields two main quantitative outputs: the amount of fuel and
time it takes to complete the task of cooking a standardized meal. The CCT was chosen as the
performance test for this study because it can be completed in a relatively short timeframe, and it
provides a standardized comparison using parameters of local fuel, food, and cooking practices. The
performance outcomes from the CCTs provide an indication of the potential these stoves have when
used in homes participating in the larger study. The larger study will include assessments of daily
household fuel consumption and stove usage to verify which stoves have the greatest impacts in
homes.
1.2 Study Location
The Renewable Energy Test Station (RETS) in
and associated training from March 2nd to M
Academy of Science and Technology, and
conducts the certification tests for products
and components, including household
stoves, being disseminated by the
Alternative Energy Promotion Center
(AEPC). AEPC, which manages government
efforts for improving rural household
energy access, provided logistical support
along with Winrock. The tests were
conducted in the courtyard of RETS, with
stations set up for each cook, as well as for
food preparation, food serving, and
dishwashing (Figure 1).
Lalitpur, Nepal hosted the stove performance testing
arch 12th of 2015. RETS is overseen by the Nepal
Figure 1. RETS outdoor courtyard, where CCTs were conducted.
7 Controlled Cooking Test Results
2. Methods
2.1 Study Overview
A total of 168 CCTs (28 tests per stove) were
g the study. The CCTs were
ght cooks who were recruited from
es outside of Kathmandu (Figure
re trained how to use the new
inrock technical team and were
practice cooking with each stove
fore the CCTs were conducted.
RETS, AEPC, Winrock, and CRT/N
Berkeley Air staff on conducting
quality assurance/control
before the formal testing started.
l other assistants from the local
tting the vegetables, washing
chopping the wood.
technicians over time to minimize
alternated individual CCTs
e/fuel practices changing as cooks
structure also helped guard
completed durin
conducted by ei
rural communiti
2). The cooks we
stoves by the W
given ten days to
in their home be
Technicians from
were trained by
CCTs, including food and fuel weighing techniques, data entry, and
procedures. A full practice test was also conducted with the cooks
In addition to the technicians and cooks, the team included severa
community and RETS, who helped with critical activities such as cu
dishes between tests, shopping for food in the local markets, and
The sampling schedule was structured to rotate stoves, cooks, and
potential bias in stove performance results. Specifically, the cooks
between the stoves, mitigating against the potential effect of stov
became more comfortable with the CCT procedures. This sampling
against changes in weather and fuel moisture content, which also varied on a daily basis. Finally, the
technicians and cooks were also rotated to ensure that any effect from specific cook‐technician
interactions would be spread out evenly among the different stoves. The sampling schedule for day
two is provided in Table 2 and the full schedule can be found in Appendix 6.1.
2.2 Food and Pots
The standard meal was decided by consulting
with the Nepalese technical team on what
food would be representative of the region,
which was determined to be rice, daal
(lentils), and a vegetable dish consisting of
cauliflower, potatoes, onions, tomatoes, and
spices (Figure 3). The rice, daal, and
vegetables were pre‐weighed and prepared
in quantities that represented a typical meal
for a family of four. Cooks used water, oil,
ghee, and spices as desired to complete the
dishes. The details of the ingredients and
quantities are shown in Appendix 6.2.
Figure 2. The cooks take a break from the CCTs for tea.
Table 2. Sampling schedule for day 2 of the CCTs.
Station Cook
AS GW 1 EC 1 LC 1
PD XU 2 GW 2 EC 2
NG PR 3 XU 3 GW 3
ST TC 4 PR 4 XU 4
UT LC 5 TC 5 PR 5
SM EC 6 LC 6 TC 6
LP GW 7 EC 7 LC 7
DG XU 8 GW 8 EC 8SM
Stove (replicate)
DAY 2 (Friday, 2015/03/06)
BP
NJ
BK
Note: “Station” denotes the technician’s initials and “Cook” denotes the cook’s initials
8 Controlled Cooking Test Results
Figure 3. Vegetables and spices on aluminum plates (left), a field technician pre‐weighing daal (right).
Food was cooked in three vessels: an aluminum flat‐bottom pot with a lid for rice, an aluminum
round‐bottom pot for vegetables (kadhai), and an aluminum pressure cooker (2 liter capacity) for
daal (Figure 4). All stoves were able to accommodate all cooking pots with the caveat that the local
chimney stove required a piece of wood to fill a small gap between the pressure cooker and pot‐hole
wall. The only specific instruction the cooks were provided with for meal preparation was to use the
lid for cooking rice, which is typical practice in the region. The total food cooked was determined at
the end of the meal by weighing each of the prepared dishes (pot weights were subtracted) and
summing the masses. The mean amount of food cooked per meal was 4181 g with a standard
deviation of 274 g.
Figure 4. Aluminum wok for vegetables (far left), aluminum pot with lid for rice (middle), and pressure cooker for daal (right).
2.3 Fuel
All tests were conducted using wood sourced from a local merchant and consisted of two hard‐
woods commonly used in Nepal: Gogan (Saurauia napaulensis), a shallow‐rooted fruiting tree, and
wild Himalayan cherry tree (Prunus cerasoides).
The wood was cut into pieces with circumferences of approximately 12‐18 cm and differing lengths
of 15 to 60 cm, as appropriate for each stove. For the top‐loading Eco‐Chulha, wood was cut into
smaller pieces, approximately 5‐10 cm long and 8‐12 cm in circumference. Cooks were provided with
kerosene and shredded paper to aid in starting the stoves. These fuels helped provide relatively
consistent fire starting during the CCTs and are used in rural Nepal, although small twigs, crop
residues, and other materials are also commonly used to aid in fire‐starting.
Before each test, the field staff formed pre‐weighed bundles of wood fuel that were approximately 3
kg. After the food was cooked, the leftover wood, charcoal, and ash were collected and weighed.
The weights of the cooked foods in their receptacles were also recorded. The time the fire was lit,
9 Controlled Cooking Test Results
the start and end times for each dish cooked, and the time the fire was extinguished were recorded.
All data was recorded by field technicians on the field sampling form (Appendix 6.5).
Wood moisture was measured twice daily, once before the CCTs and once after, using a dual pin
Extech MO120 moisture meter at three points on seven randomly selected sticks in the woodpile.
The moisture readings were recorded on a sampling form (Appendix 6.3) and then transcribed into
the database. The average moisture content during the CCTs was 17.6±3.1%, with daily means
ranging from 20.7% on the first day to 15.2% on the final day.
Specific fuel consumption was used as a normalized measure of fuel use, defined as the equivalent
dry wood used divided by the final amount of food cooked. The “equivalent dry wood consumed”
normalizes the amount of wood used to complete the CCT for two factors: the amount of moisture
in the wood and the amount of charcoal that remains unburned after the cooking task is complete.
The standard units of specific consumption are grams of equivalent dry wood used per kilogram of
food cooked (g/kg).
Specific fuel consumption (SC) was calculated as follows:
SC = fd/Wf
where Wf is the weight of the cooked food (kg), and fd is the equivalent dry wood consumed (g). fd
adjusts for the energy used to vaporize moisture in the wood as well as the amount of charcoal left
in the stove when cooking is finished with the following equation:
fd = (fi – ff)(1‐[1.12m]) – 1.5Δcc
where fi is the initial wood weight, ff is the final wood weight, m is the moisture content on a wet
basis, and ∆cc is the weight of the remaining char (CCT 2.0 Protocol).
Firepower was calculated by converting the wood mass to its energy equivalent1 and dividing by the
amount of time it took to complete a given test.
2.4 Description of Cookstoves
The five new stove models and the traditional chulho tested in the study are described in Table 3
below. The traditional chulho was a three‐stone‐fire, which the local technical team reported to be
the most common baseline stove for the WASHplus study area. Other common traditional stove
types in the region include metal tripods and simple open stoves constructed of mud.
1 18.130 MJ/kg was assumed as the energy density of the dry wood equivalent, based on WBT 4.2.3 protocol.
10 Controlled Cooking Test Results
Table 3. Specifications and photos of stove types
Stove Model and Specifications
Traditional chulho
Local modification of the three stone fire
Materials: Clay bricks
Weight: 22.6 kg
Height: 15.6 cm
Other features/descriptors: Constructed
out of 6 clay bricks, 2 stacked bricks
composed each ‘stone.’
Eco‐Chulha XXL Single pot, portable, fan gasifier stove
Weight (with stand): 5.8 kg
Materials: Stainless steel
Height: 33 cm
Combustion chamber diameter: 16 cm
Website: http://www.ecochula.co.in/
Local chimney stove
Two pot, built‐in, clay and clay brick
chimney stove
Materials: Iron rod, chimney outlet, chimney blocks, mud bricks
First pot diameter: 19.5 cm
Second pot diameter: 15.5 cm
Height: 22 cm at first pot and 27 cm at second pot, from base.
Length: 91 cm
Width: 40 cm
Chimney heights: 58 cm (version a) and 79 cm (version b), measured from second pot
.
Stove Image
11 Controlled Cooking Test Results
Stove Model and Specifications
Xunda Field Dragon Single pot, portable, rocket design stove
Weight: 5.94 kg
Materials: Surface ‐ 0.4mm stainless steel, cylinder ‐ 1.5 mm stainless steel
Height: 31 cm
Combustion chamber diameter: 9.0 cm
Model number: Field Dragon, Model No. C1.5‐SW‐IZ
Website: http://www.xundaco.com/
Greenway Jumbo
Single pot, portable, natural draft, gasifier stove
Steel and aluminum with Bakelite handles
Weight: 3.8 kg
Height: 29 cm
Combustion chamber diameter: 11 cm
Model number: JS1
Website: http://www.greenwayappliances.com/
Stove Image
12 Controlled Cooking Test Results
Stove Model and Specifications
Prakti Double Burner Wood Stove with
Chimney
Two pot, portable, metal chimney stove.
Materials: Stainless steel, seamless steel, iron sheet
Weight: 7.12 kg (stove), 8.92 kg (stove and chimney)
Height: 27 cm (stove), 193 cm (stove and chimney)
Chimney diameter: 7 cm
Combustion chamber diameter: 12 cm
Other features/descriptors: Flexible pot rest, chimney adaptor
Website: http://praktidesign.com/
Stove Image
All of the new stoves except the local chimney stove have metal combustion chambers where the
fire is contained. The local chimney stove’s combustion chamber is formed from clay and mud‐
bricks. All stoves burn wood and can accommodate other biomass fuels such as twigs and leaves to
varying degrees. All stoves except the Eco‐Chulha are fueled through an opening at the base of the
stove. The Eco‐Chulha is fueled from the top, can be loaded with a batch of fuel before lighting the
stove, and, as needed, additional pieces of fuel can be slid into the opening between the pot and the
stove body, or the stove can be slid out from under the pot stand to add larger amounts of fuel.
The Prakti, Greenway, Xunda, local chimney stove, and traditional chulho are all designed to burn
fuel in a single combustion stage. The Eco‐Chulha, a forced‐air gasifier, is designed to employ a two‐
stage process where the wood undergoes pyrolysis in the lower part of the combustion chamber and
then a second influx of air towards the top of the stove mixes and burns the gases released in the
first stage.
2.5 Quality Control and Assurance
The four digital scales used for fuel mass measurement (My Weigh 7001DX) underwent a 5‐point
calibration check using NIST certified mass standards in the Berkeley Air laboratory in Berkeley, CA
(r2>0.999). All scales were checked daily and at the end of the field survey to ensure the standard
13 Controlled Cooking Test Results
weight measurement was within 1% of the known mass, verifying measurement precision. An
additional scale from RETS was used for food mass, and was found to be within 0.2% of the Berkeley
Air scales based on the standard weight. An example of the scale check can be found in Appendix
6.4. Moisture meters were checked every mornin
Data was entered onto survey forms during CCTs
(Appendix 6.5) and then transcribed into an
online database. The database was reviewed
daily for transcription errors and illogical entries.
Subsequent cross‐checks of the hard‐copy
survey form and the database were performed
to correct errors as needed, and a final data
review was done to check for outliers of
firepower, cooking time, food weights, and
specific consumption.
3. Results
3.1 Specific Consumption
All five new stoves significantly reduced fuel use c
ranging from 29‐47% (Table 4). The Eco‐Chulha a
47% and 45% less fuel than the traditional chulho
g as per the manufacturer’s verification tests.
ompared to the baseline technology, with savings
nd Xunda were the most fuel efficient stoves, using
, respectively, while the Greenway and Prakti
stoves both used 40% less. The local chimney stove had the greatest specific consumption of the
new stoves, but was still 29% more fuel efficient than the baseline technology.
Table 4. Summary statistics of the specific consumption values indicate statistical significance.
estimates from the CCTs. Bolded differences and p‐
Specific Consumption (g wood / kg food)
Trad Chulho Greenway Prakti Xunda Eco‐Chulha Local Chimney
Mean 328 197 197 179 173 234
Median 316 192 197 179 171 233
Standard Deviation 56 36 26 37 22 30
Standard Error 11 7 5 7 4 6
CoV 17% 18% 13% 21% 13% 13%
Upper 95% CI
Lower 95% CI
349
307
211
184
207
187
193
165
181
165
245
223
N 28 28 28 28 28 28
Mean Difference ‐‐ ‐40% ‐40% ‐45% ‐47% ‐29%
P‐value ‐‐ <0.01 <0.01 <0.01 <0.01 <0.01 Notes: Statistical significance was determined using an unpaired Student’s t‐test. P‐values of less than 0.05 “statistically significant” and indicate that there is greater than 95% likelihood that the difference between measured values did not occur by chance. CoV = coefficient of variation, defined as the standard deviation/mean. CI = confidence interval.
are the
considered two
The box plots of specific consumptions show the differences in fuel efficiency as well as illustrate
their performance variability (Figure 6). The traditional chulho’s specific consumption had a
substantially wider distribution than those for the new stoves, with an interquartile range of 79 g
food / kg wood, compared to less than 45 g food / kg wood for all of the new stoves. The tighter
Figure 5. The CCT team reviewing data entry during the first day of CCTs.
14 Controlled Cooking Test Results
distributions for the new stoves are likely due to having enclosed combustion chambers, which help
control the fire and limit impacts from wind. There were some specific tests with the new stoves
which did show that large variation in performance is possible. The Xunda’s 5th and 95th percentiles,
for example, ranged from 105 to 240 g food / kg wood, respectively. In general, however, the
variability for specific consumption estimates observed in this study was relatively low. The
coefficients of variation ranged from 13% to 21%, which are on the lower end compared to those
reported for CCTs in Kenya (21%‐33%) (Pennise et al., 2010) and Mexico (10‐27%) (Berrueta et al.,
2008).
450
ption
od) 400
m fo 350
Consu /kg
300
cific
(gwood
250
Spe 200
150
10095th percentile 50 75th
0Median
percentile
25th percentile
5th percentile
Figure 6. Boxplots showing the distribution of specific consumption for each stove. A guide to the box plot can be found in the lower right hand corner of the figure.
3.2 Cooking Time
All of the stoves significantly reduced cooking times compared to the traditional chu
Mean cooking time for the local chimney stove was the lowest (43 min), a third less
traditional chulho (64 min). The other two‐pot stove, the Prakti, had the second low
(50 min, 23% savings), suggesting the ability to simultaneously cook two dishes was
factor in reducing the overall cooking time. All of the new, single‐pot cooking stoves
time by 15%, due solely to their ability to cook single dishes more quickly than the tr
The distributions of cooking times shown in the boxplots (Figure 7) also illustrate th
cooking times achieved by the new stoves. The variability in cooking times, although
of 10‐17%), was substantial enough to result in some overlap of cooking time distrib
most of the new stoves and the traditional chulho. This variability was likely due to
lho (Table 5).
than the
est cooking time
a significant
reduced cooking
aditional chulho.
e reduced
not large (CoV’s
utions between
normal variation
n user operation, as well differences in fuel and environmental conditions (e.g. moisture content
nd wind).
i
a
15 Controlled Cooking Test Results
Table 5. Summary statistics of the cooking indicate statistical significance.
time estimates from the CCTs. Bolded differences and p‐values
Cooking time (minutes)
Trad Chulho Greenway Prakti Xunda Eco‐Chulha Local Chimney
Mean 64 55 50 54 55 43
Median 64 53 51 54 53 41
Standard Deviation 8 7 9 6 9 7
Standard Error 2 1 2 1 2 1
CoV 13% 14% 18% 10% 17% 16%
Upper 95% CI 67 58 53 56 58 46
Lower 95% CI 61 52 46 52 51 41
N 28 28 28 28 28 28
Mean Difference ‐‐ ‐15% ‐23% ‐15% ‐15% ‐33%
P‐value ‐‐ <0.01 <0.01 <0.01 <0.01 <0.01 Notes: Statistical significance was determined using an unpaired Student’s t‐test. P‐values of less than 0.05 “statistically significant” and indicate that there is greater than 95% likelihood that the difference between measured values did not occur by chance. CoV = coefficient of variation, defined as the standard deviation/mean. CI = confidence interval.
are the
considered two
0
10
20
30
40
50
60
70
80
90
Cooking Time (m
inutes)
Figure 7. Boxplots showing the distribution of cooking time for each stove. A guide to the box plot can be found in the lower right hand corner of the figure.
95th percentile
75th percentile
Median 25th percentile
5th percentile
3.3 Firepower
Firepower, or the energy consumed per unit time (kilojoules/second [kW]), provides an indication of
how stoves are being operated. The range of mean firepowers observed here (4.1‐7.0 kW) (see Table
6) are in line with those reported during other laboratory and field studies. Woodfuel cookstoves
from Jetter et al.’s (2012) laboratory tests had mean firepowers ranging from ~2.5‐7 kW, and
Johnson and Garland (2014) presented field based estimates of ~3‐8 kW for similar stove types. The
similar firepower ranges between this and other studies indicate that the stoves were being
operated normally by the CCT cooks.
16 Controlled Cooking Test Results
Table 6. Summary indicate statistical
statistics of the firepower estimates significance.
from the CCTs. Bolded differences and p‐values
Firepower (kW)
Trad Chulho Greenway Prakti Xunda Eco‐Chulha Local Chimney
Mean 6.6 4.6 5.1 4.1 4.1 7.0
Median 6.5 4.6 5.0 4.1 4.1 6.8
Standard Deviation 1.1 0.8 0.9 0.8 0.6 1.3
Standard Error 0.2 0.1 0.2 0.2 0.1 0.2
CoV 16% 17% 18% 21% 16% 18%
Upper 95% CI 7.0 4.8 5.5 4.4 4.3 7.5
Lower 95% CI 6.2 4.3 4.8 3.8 3.8 6.6
N 28 28 28 28 28 28
Mean Difference ‐‐ ‐31% ‐23% ‐38% ‐39% 6%
P‐value ‐‐ <0.01 <0.01 <0.01 <0.01 0.20 Notes: Statistical significance was determined using an unpaired Student’s t‐test. P‐values of less than 0.05 “statistically significant” and indicate that there is greater than 95% likelihood that the difference between measured values did not occur by chance. CoV = coefficient of variation, defined as the standard deviation/mean. CI = confidence interval.
are the
considered two
Higher firepowers are generally associated with lower thermal efficiency as more energy needs to be
consumed to result in the same energy delivered to the pot (Jetter et al., 2012; Johnson and
Garland, 2014). The firepowers observed for this study generally followed this trend (see Figure 6
and Figure 8), with the most fuel efficient stoves (Xunda and Eco‐Chulha) having been operated at
the lowest mean firepower (4.1 kW). The much less efficient traditional chulho was operated at
significantly higher firepower (6.6 kW). The local chimney stove, which was 29% more fuel efficient
than the traditional chulho, was an exception, with the highest mean firepower (7.0 kW). The reason
for this exception is almost certainly that while the local chimney stove consumed more energy per
unit time than the traditional chulho, it was also able to transfer more of that released energy into
cooking food due to its two‐pot configuration.
0
1
2
3
4
5
6
7
8
9
10
Firepower (kW
)
Figure 8. Boxplots showing the distribution of firepower for each stove. A guide to the box plot can be found in the lower right hand corner of the figure.
95th percentile
75th percentile
Median 25th percentile
5th percentile
17 Controlled Cooking Test Results
4. Implications for field study
Overall, the specific consumption and cooking time results are promising given the reductions
relative to the traditional chulho. The results suggest that the best performing stoves could result in
nearly 50% fuel savings in homes, which would provide substantial household‐level and
environmental benefits. It is important to note, however, that these benefits will be a function of
performance and usage. A recent paper by Johnson and Chiang (in press) presented a framework
which modeled how different stove performance‐usage scenarios translate into varying levels of
health and environmental impacts. By combining the CCT results found here, with the approach
described in Johnson and Chiang (in press), we estimated the fuel consumption savings shown in
Figure 9. The modeled fuel savings estimates
show, for example, that the extent to which
the Eco‐Chulha or Xunda displaces the
traditional chulho is going to be far more
important than the small difference in savings
due to their performance. The graph also
illustrates that there are scenarios for which
the local chimney stove could provide the
greatest benefits, should it almost entirely
displace the traditional chulho, versus the
other higher performing stoves, should they
only displace the traditional chulho by ~60%
or less. While these are only modeled
estimates, they illustrate the importance that
user preference, and thereby usage of the
new stove and displacement of the traditional
chulho, will have on the household‐level
impacts. This assessment of user preference is
a main focus of the WASHplus study.
Figure 9. Modeled relationships between three‐stone‐fire displacement and fuel savings for different performance‐usage scenarios, estimated using the CCT specific consumption results and the percent displacement of the traditional chulho.
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
0% 20% 40% 60% 80% 100%
Fuel savings
Percent displacement of traditional chulho by new stove
Eco‐Chulha
Xunda
Prakti and Greenway
Local Chimney
18 Controlled Cooking Test Results
5. References
Bailis, R., 2007. Controlled Cooking Test Protocol: Version 2.0. Berrueta, V.M., Edwards, R.D., Masera, O.R., 2008. Energy performance of wood‐burning cookstoves
in Michoacan, Mexico. Renew. Energy 33, 859–870. Jetter, J., Zhao, Y., Smith, K.R., Khan, B., Yelverton, T., DeCarlo, P., Hays, M.D., 2012. Pollutant
Emissions and Energy Efficiency under Controlled Conditions for Household Biomass Cookstoves and Implications for Metrics Useful in Setting International Test Standards. Environ. Sci. Technol. 46, 10827–10834. doi:10.1021/es301693f
Johnson, M.A., Chiang, R.A., in press. Quantitative Guidance for Stove Usage and Performance to Achieve Health and Environmental Targets. Environ. Health Perspect. doi:10.1289/ehp.1408681
Johnson, M., Garland, C., 2014. Emissions performance of cookstoves in Asia and Africa. Pennise, D., Charron, D., Wofchuck, T., Rouse, J., Hunt, A., 2010. Evaluation of Manufactured Wood
Stoves in Dadaab Refugee Camps, Kenya. United States Agency for International Development.
19 Controlled Cooking Test Results
6. Appendices
6.1 Daily Scheduling Matrix
Full schedule for the CCTs. The cooks alternated between all 6 stoves to minimize the potential
effect of behavioral changes over time.
Technician, Cook, Stove (Test, Replicate ID)
Tech Cook Wednesday Tech Cook Friday Tech Cook Sunday
AS TC 1 PR 1 XU 1 AS GW 1 EC 1 LC 1 AS TC 9 PR 9 XU 9NJ BP SM
PD LC 2 TC 2 PR 2 PD XU 2 GW 2 EC 2 PD LC 10 TC 10 PR 10NG EC 3 LC 3 TC 3 NG PR 3 XU 3 GW 3 NG EC 11 LC 11 TC 11
BK NJ BPST GW 4 EC 4 LC 4 ST TC 4 PR 4 XU 4 ST GW 12 EC 12 LC 12UT XU 5 GW 5 EC 5 UT LC 5 TC 5 PR 5 UT XU 13 GW 13 EC 13
SM BK NJSM PR 6 XU 6 GW 6 SM EC 6 LC 6 TC 6 SM PR 14 XU 14 GW 14LP TC 7 PR 7 XU 7 LP GW 7 EC 7 LC 7 LP TC 15 PR 15 XU 15
BP SM BKDG LC 8 TC 8 PR 8 DG XU 8 GW 8 EC 8 DG LC 16 TC 16 PR 16
Tech Cook Monday Tech Cook Tuesday Tech Cook Wednesday
AS GW 9 EC 9 LC 9 AS TC 17 PR 17 XU 17 AS GW 17 EC 17 LC 17BK NJ BP
PD XU 10 GW 10 EC 10 PD LC 18 TC 18 PR 18 PD XU 18 GW 18 EC 18NG PR 11 XU 11 GW 11 NG EC 19 LC 19 TC 19 NG PR 19 XU 19 GW 19
SM BK NJST TC 12 PR 12 XU 12 ST GW 20 EC 20 LC 20 ST TC 20 PR 20 XU 20UT LC 13 TC 13 PR 13 UT XU 21 GW 21 EC 21 UT LC 21 TC 21 PR 21
BP SM BKSM EC 14 LC 14 TC 14 SM PR 22 XU 22 GW 22 SM EC 22 LC 22 TC 22LP GW 15 EC 15 LC 15 LP TC 23 PR 23 XU 23 LP GW 23 EC 23 LC 23
NJ BP SMDG XU 16 GW 16 EC 16 DG LC 24 TC 24 PR 24 DG XU 24 GW 24 EC 24
Tech Cook Thurday
AS TC 25 PR 25 XU 25SM
PD GW 25 EC 25 LC 25NG LC 26 TC 26 PR 26
BPST XU 26 GW 26 EC 26UT EC 27 LC 27 TC 27
NJSM PR 25 XU 27 GW 27LP GW 28 EC 28 LC 28
BKDG TC 28 PR 26 XU 28
Note: TC = Traditional Chulho, PR = Prakti. XU = Xunda, GW = Greenway, EC = Eco‐Chulha, LC = Local chimney stove
(Johnson and Chiang, in press)
20 Controlled Cooking Test Results
6.2
Standard Meal Details
Ingredient Initial Mass
Rice
Daal
Cauliflower
Potatoes
Tomatoes
Onion
Turmeric, coriander, cumin, salt, chili powder, garlic, ginger, and ghee
Oil
Water
800g
200g
~Half a head
~1 large or 2 small
~6 small tomatoes
~1 small
Cook’s discretion
Cook’s discretion
Cook’s discretion
6.3 Wood Moisture Sampling Form
Day 1 Morning Date (YY/MM/DD):
stick1 stick1 stick1 stick2 stick2 stick2 stick3 stick3 stick3 stick4 stick4 stick4
stick5 stick5 stick5 stick6 stick6 stick6 stick7 stick7 stick7
Day 1 Evening
stick1 stick1 stick1 stick2 stick2 stick2 stick3 stick3 stick3 stick4 stick4 stick4
stick5 stick5 stick5 stick6 stick6 stick6 stick7 stick7 stick7
21 Controlled Cooking Test Results
6.4 Scale Calibration and Maintenance
Table 7. Example of scale maintenance database (data from day 1 of CCTs shown).
Scale: 1.
2.
3.
Daily Check At the beginning of the study each of the technicians need to pick a standard will not change mass and enter into column M Every day, the technician should enter initials, date, scale ID number, and standard mass reading to ensure the scales are not drifting If % difference in column J is red, try re‐weighing the standard weight again. If still red, recalibrate scale.
weight that
Difference will recalibration is
display red when required (>2%)
Tech Date ID/Serial number
X kg reading
Standard Mass kg
Slope Adjustment
Intercept Adjustment
Adjusted X kg reading
Difference
RS 3/4/2015 TS_1 2455 2456 1.0002 0.0001 2456 0.0%
RS 3/4/2015 TS_2 2454 2456 0.9997 0.0006 2453 0.1%
RS 3/4/2015 TS_3 2456 2456 1.0001 0.0001 2456 0.0%
RS 3/4/2015 TS_4 2453 2456 0.9998 0.0002 2453 0.1%
RS 3/4/2015 RETS1 2462 2456 1.0000 0.0000 2462 0.2%
22 Controlled Cooking Test Results
6.5 Field Sampling Form
Controlled Cooking Test Form – Nepal, 2015
A. Test Data Stove Type Codes TEST ID:
A1 Date (YY/MM/DD) TC Traditional chulho
(STOVEID_COOKID_TECHID_REP#). A2 Technician ID RS / NJ / BK / SM / BP PR Prakti
A3 Cook ID AS / PD / NG / ST / UT / SM / LP / DG XU Xunda Example: TCa_LS_PT_7
TCa TCb / PRa PRb / XUa XUb A4 Stove GW Greenway
GWa GWb / ECa ECb / LCa LCb The replicate# can be found on the daily
A5 Raining Y / N EC EcoChulha sampling plan sheet for each station.
A6 Wind Condition 1. calm / 2. light breeze / 3. strong wind LC Local chimney
B. Food Weights Empty container (g) Container with food (g) Soaked
B1 Dry daal Y / N
B2 Cooked daal
B3 Dry rice Y / N
B4 Cooked rice
B5 Uncooked vegetables
B6 Cooked vegetables
(HH:MM) C. Fuel Weights Empty container (g) Container with fuel (g) D. Times
24 hr format
C1 Initial weight of wood Activity Start End
C2 Final weight of remaining wood D1 CCT
C3 Weight of leftover char D2 Daal
C4 Weight of leftover ash D3 Rice
C5 Initial weight of starter paper D4 Veg
C6 Final weight of starter paper
23 Controlled Cooking Test Results
6.6 Field team
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